Pneumatic tire

Abstract

A middle land portion includes middle sipes and middle lateral grooves. A shoulder land portion includes shoulder lateral grooves and shoulder sipes. A ratio Ems/Ema is smaller than a ratio Ess/Esa. Ems denotes a total of elements of edge lengths of the middle sipes in an axial direction of the tire. Ema denotes a total of elements of edge lengths of the middle sipes and the middle lateral grooves in the axial direction. Ess denotes a total of elements of edge lengths of the shoulder sipes in the axial direction. Esa denotes a total of elements of edge lengths of the shoulder sipes and the shoulder lateral grooves in the axial direction.

What is claimed is: 
     
       1. A pneumatic tire comprising:
 a tread portion, the tread portion provided with a pair of circumferentially and continuously extending crown main grooves each disposed on both sides of a tire equator and a pair of circumferentially and continuously extending shoulder main grooves disposed axially outside the crown main groove to form a crown land portion disposed between the pair of crown main grooves, a pair of middle land portions each disposed between the crown main groove and the shoulder main groove on each side of the tire equator, and a pair of shoulder land portions each disposed axially outside the shoulder main groove on each side of the tire equator, 
 the crown land portion being provided with a plurality of crown lateral grooves each extending from the crown main groove toward the tire equator without entirely passing through the crown land portion, 
 each of the middle land portions being provided with a plurality of middle lateral grooves each extending from the shoulder main groove toward the crown main groove without entirely passing through the middle land portion and a plurality of middle sipes arranged between circumferentially adjacent middle lateral grooves, 
 the middle sipes comprising a first middle sipe extending entirely across the middle land portion and a second middle sipe extending partially across the middle land portion, the first middle sipe communicating directly with the crown main groove, wherein an overlapped distance (L 4 ) between an axially inner end of the first middle sipe and an axially outer end of one of the circumferentially adjacent middle lateral grooves in a circumferential direction of the tire is greater than an overlapped distance (L 5 ) between an axially outer end of the first middle sipes and an axially inner end of the other one of the circumferentially adjacent middle lateral grooves in the circumferential direction of the tire, and 
 each of the shoulder land portions being provided with a plurality of shoulder lateral grooves each extending axially inward from a tread edge without entirely passing through the shoulder land portion, and a plurality of shoulder sipes each arranged between the circumferentially adjacent shoulder lateral grooves, 
 wherein a ratio Ems/Ema is smaller than a ratio Ess/Esa, where Ems denotes a total of elements of edge lengths of the middle sipes in an axial direction of the tire, Ema denotes a total of elements of edge lengths of the middle sipes and the middle lateral grooves in the axial direction of the tire, Ess denotes a total of elements of edge lengths of the shoulder sipes in the axial direction of the tire, and Esa denotes a total of elements of edge lengths of the shoulder sipes and the shoulder lateral grooves in the axial direction of the tire. 
 
     
     
       2. The pneumatic tire according to  claim 1 , wherein each of the middle sipes and the shoulder sipes has an arc-shape. 
     
     
       3. The pneumatic tire according to  claim 1 , wherein each angle of the middle sipes and the shoulder sipes with respect to a circumferential direction of the tire gradually increases toward its axially outer end from its axially inner end. 
     
     
       4. The pneumatic tire according to  claim 1 , wherein one of the shoulder land portions is further provided with a plurality of shoulder auxiliary sipes each communicating between an axially inner end of the shoulder lateral groove and the shoulder main groove. 
     
     
       5. The pneumatic tire according to  claim 1 , wherein a sipe is absent in the crown land portion. 
     
     
       6. The pneumatic tire according to  claim 1 , wherein a total edge length of the middle sipes and shoulder sipes is set in a range of from 40% to 70% of a total edge length of the crown main grooves, the shoulder main grooves, the crown lateral grooves, the middle lateral grooves, the shoulder lateral grooves, the middle sipes, and the shoulder sipes. 
     
     
       7. The pneumatic tire according to  claim 1 ,
 wherein a number of the middle lateral grooves in each middle land portion is in a range of from 56 to 72, and 
 a number of the shoulder lateral grooves in each shoulder land portion is in a range of from 56 to 72. 
 
     
     
       8. The pneumatic tire according to  claim 1 , wherein a number of the shoulder lateral grooves in each shoulder land portion is smaller than a number of the middle lateral grooves in each middle land portions. 
     
     
       9. The pneumatic tire according to  claim 1 , wherein the crown lateral grooves and the shoulder lateral grooves are inclined in a same direction. 
     
     
       10. The pneumatic tire according to  claim 1 , wherein each of the crown main grooves and the shoulder main grooves extends straightly in the circumferential direction of the tire. 
     
     
       11. The pneumatic tire according to  claim 1 , wherein the overlap length (L 4 ) and the overlap length (L 5 ) are in a range of from 8% to 15% of placement pitches (P 2 ) of the first middle sipes.